Contribution of human short‐wave cones to luminance and motion detection.

Abstract

SUMMARY1. Human short-wave S cone signals are important for colour vision and here we examine whether the S cone signals also contribute to motion and luminance.2. Detection was measured with moving patterns that selectively stimulated S cones -violet sine-wave gratings of 1 cycle deg-' on an intense yellowish field. For rates up to 12 Hz, detection was governed by non-directional mechanisms, possibly of a chromatic nature, as shown by three findings: moving gratings had to be suprathreshold for their direction to be identified; the threshold ratio of counterphase flickering versus moving gratings was low; and direction-selective adaptation was essentially absent. 3. Evidence for less sensitive, directional mechanisms includes the following: at high velocity, the direction of movement of the violet gratings can be identified just slightly above the detection threshold; directional adaptation was strong with a suprathreshold test pattern; velocity was seen veridically for clearly suprathreshold patterns; and a counterphase flickering test, added in spatial-temporal quadrature phase to a similar suprathreshold mask, had identical detection and directionidentification thresholds.4. Interactions of long-wave L cone and S cone signals in direction-selective mechanisms were measured with an orange counterphase grating and a violet counterphase test, both flickering at the same rate and presented in spatial quadrature phase on the yellowish adapting field. Direction identification thresholds, measured as a function of the temporal phase of two gratings, demonstrated both that the S cone signal lags considerably behind the L cone signal (an effect that strongly varies with S cone light adaptation), and more strikingly, the S cone signal summates with a negative sign and thus is effectively inverted in direction-selective mechanisms.5. Quantitatively similar temporal phase functions were obtained with uniform violet and orange flicker when a luminance discrimination criterion was used: thus the S cone signal summates negatively with the L cone signal for both discrimination of luminance flicker and the direction of motion.6. The temporal phase functions accurately predicted threshold summation for * To whom correspondence should be sent. J. LEE AND C. F. STROMEYER IIIidentifying the direction of motion of a pair of violet and orange gratings moving with the same velocity but with different spatial phase offsets. Once the relative temporal phase lag of the S cones was compensated for, there was linear threshold summation for the violet and orange patterns when presented in effective (physiological) spatial antiphase, and clear cancellation when presented in phase. This and related experiments show a linear summation of S, M and L cone signals for direction detection, with the S cones having a negative sign. The luminance contrast sensitivity is very high for the spectrally long-wave member of the pair of gratings (300-500 at 8 Hz), suggesting that the patterns are detected with high-contrastsensitivity mechanisms such as ...

Opponent melanopsin and S-cone signals in the human pupillary light response

“…Similar to our findings in the pupil response, there is evidence of S-cone opponency in the perception of the luminance of stimuli (35,36). In the pupil response, we find that S-cone signals oppose the sum of melanopsin and L+M signals, which we term here pupil "brightness."…”

Faster than the eye can see: blue cones respond to rapid flicker

“…5). A similar distinction between a chromatic and a luminance S-cone pathway was made by Lee and Stromeyer 20 on the basis of motion experiments.…”

“…This blue-cone luminance input is characterized by a bandpass temporal-frequency response that extends to nearly 30 Hz, 5 22 the ability to flicker-photometrically cancel flicker generated in the green or red cones, 5 and the ability to provide information regarding the direction of the motion of moving gratings, 20 all of which distinguish the blue-cone luminance input from the blue-cone chromatic input (see Refs. 5,20, and 23 for further experiments and discussion). By measuring the signals of the blue cones and those of the red and green cones through a common pathway, the luminance pathway, it should be possible to compare directly the temporal properties of the three cone types.…”

The mechanism of isoluminant chromatic motion perception

“…On the other hand, although it has occasionally been stated that there is no isoluminant motion perception (ref. 13, p. 161), there are obvious demonstrations from human psychophysics of the perceived motion of isoluminant stimuli (14)(15)(16). Although the various degradations of motion perceived in isoluminant stimuli have led to speculations about special mechanisms for chromatic motion (17)(18)(19)(20)(21), lack of convincing experimental paradigms and results has left completely unresolved the question of how and where isoluminant motion might be computed, and there are supporters for all theoretical stands (22)(23)(24)(25)(26)(27)(28)(29).…”